A variety of pharmacological, neuroanatomical, electrophysiological, and behavioral data suggest that central and peripheral systems involved in the regulation of blood pressure are physiologically linked to endogenous pain-regulatory systems. This network is proposed to govern the elaboration of adaptive responses of an organism to aversive environmental stimulation. The specific aims of the present research proposal are to establish fundamental relationships that exist between these systems by generating behavioral and physiological profiles of several models of hypertensive rats and their associated normotensive controls in tests of nociception. The behavioral profiles will be generated by assessments of (1) basal and stress-induced levels of responsivity in hot-plat, tail-flick, and flinch-jump analgesiometric assays, and (2) acquisition of conditioned suppression of instrumental responding. The physiological profiles will be generated by (1) measurements of blood pressure and heart rate before, during, and after behavioral testing, and (2) assessments of baroreceptor reflex arc madulation and nociception. The hypertensive models include genetic, renal, DOCA-salt, and neurogenic, and their appropriate normotensive controls. These experiments will serve to delineate the nature of blood pressure/pain-regulatory interactions, demonstrate their biological relevance in terms of acquisition of a conditioned behavior, identify behavioral and cardiovascular marker variables through which either a proneness to or an existing state of hypertension can be identified, and suggest ways in which this network participates in diseases of adaptation. In particular, this proposal bears upon the etiology of essential hypertension on humans by considering the view that acute stress-induced elevations in arterial blood pressure resulting from exposure to either unconditioned or conditioned aversive stimuli may become sustained because barorecepto reflex arc activation of endogenous pain-inhibition systems reduces the aversiveness of environmental stimulation.